The present invention is directed to the use of bis-amines to enhance the antimicrobial activity of aqueous compositions, such as pharmaceutical compositions. The invention is particularly directed to the field of ophthalmic compositions.
Many pharmaceutical compositions are required to be sterile (i.e., free of bacteria, fungi and other pathogenic microorganisms). Examples of such compositions include: solutions and suspensions that are injected into the bodies of humans or other mammals; creams, lotions, solutions or other preparations that are topically applied to wounds, abrasions, burns, rashes, surgical incisions, or other conditions where the skin is not intact; and various types of compositions that are applied either directly to the eye (e.g., artificial tears, irrigating solutions, and drug products), or are applied to devices that will come into contact with the eye (e.g., contact lenses).
The foregoing types of compositions can be manufactured under sterile conditions via procedures that are well known to those skilled in the art. However, once the packaging for the product is opened, such that the composition is exposed to the atmosphere and other sources of potential microbial contamination (e.g., the hands of a human patient), the sterility of the product may be compromised. Such products are typically utilized multiple times by the patient, and are therefore frequently referred to as being of a “multi-dose” nature.
Due to the frequent, repeated exposure of multi-dose products to the risk of microbial contamination, it is necessary to employ a means for preventing such contamination from occurring. The means employed may be (1) a chemical agent that prevents the proliferation of microbes in the composition, which is referred to herein as an “antimicrobial preservative”; or (2) a packaging system that prevents or reduces the risk of microbes reaching the pharmaceutical composition within a container.
Multi-dose ophthalmic compositions generally must include an anti-microbial agent to prevent contamination of the compositions by bacteria, fungi and other microbes. Such compositions may come into contact with the cornea either directly or indirectly. The cornea is particularly sensitive to exogenous chemical agents. Consequently, in order to minimize the potential for harmful effects on the cornea, it is necessary to use anti-microbial agents that are relatively non-toxic to the cornea, and to use such agents at the lowest possible concentrations (i.e., the minimum amounts required in order to perform their anti-microbial functions).
Balancing the anti-microbial efficacy and potential toxicological effects of anti-microbial agents is sometimes difficult to achieve. More specifically, the anti-microbial agent concentration necessary for the preservation of ophthalmic formulations from microbial contamination or for the disinfection of contact lenses may create the potential for toxicological effects on the cornea and/or other ophthalmic tissues. Using lower concentrations of the anti-microbial agents generally helps to reduce the potential for such toxicological effects, but the lower concentrations may be insufficient to achieve the required level of biocidal efficacy (e.g., antimicrobial preservation or disinfection).
The use of an inadequate level of antimicrobial preservation may create the potential for microbial contamination of the compositions and ophthalmic infections resulting from such contaminations. This is also a serious problem, since ophthalmic infections involving Pseudomonas aeruginosa or other virulent microorganisms can lead to loss of visual function or even loss of the eye.
Thus, there is a need for a means of enhancing the activity of anti-microbial agents so that very low concentrations of the agents can be utilized without increasing the potential for toxicological effects or subjecting patients to unacceptable risks of microbial contamination and resulting ophthalmic infections.
Compositions for treating contact lenses and other types of ophthalmic compositions are generally formulated as isotonic, buffered solutions. One approach to enhancing the anti-microbial activity of such compositions is to include multi-functional components in the compositions. In addition to performing their primary functions, such as cleaning or wetting contact lens surfaces (e.g., surfactants), buffering the compositions (e.g., borate), or chelating undesirable ions (e.g., EDTA), these multi-functional components also serve to enhance the overall anti-microbial activity of the compositions. For example, ethylenediaminetetraacetic acid and the monosodium, disodium and trisodium salts thereof (collectively referred to herein as “EDTA”) has been widely used for many years in ophthalmic products, particularly products for treating contact lenses. EDTA has been used in such products for various purposes, but particularly for its supplemental anti-microbial activity and as a chelating agent. The inclusion of EDTA in contact lens care products and other ophthalmic compositions enhances the anti-microbial efficacy of chemical preservatives contained in such compositions, particularly the efficacy of those preservatives against gram negative bacteria.
The following publications may be referred to for further background regarding the use of multi-functional components to enhance the antimicrobial activity of ophthalmic compositions:    1. U.S. Pat. No. 5,817,277 (Mowrey-McKee, et al; tromethamine);    2. U.S. Pat. No. 6,503,497 (Chowhan, et al.; borate/polyol complexes);    3. U.S. Pat. No. 5,741,817 (Chowhan, et al.; low molecular weight amino acids such as glycine);    4. U.S. Pat. No. 6,319,464 (Asgharian; low molecular weight amino alcohols); and    5. U.S. Patent Application Publication No. US 2002/0122831 A1 (Mowrey-McKee, et al.; bis-aminopolyols).